Light valves have been used for over fifty years for modulation of light. A light valve may be described as a cell formed of two walls that are spaced apart by a small distance, at least one wall being transparent, the walls having electrodes thereon usually in the form of transparent conductive coatings. The cell contains a "light valve suspension" of small particles suspended in a liquid suspending medium. In the absence of an applied electrical field, the particles in the liquid suspension exhibit random Brownian movement, and hence a beam of light passing into the cell is reflected, transmitted or absorbed, depending upon the nature and concentration of the particles and the energy content of the light. When an electric field is applied through the light valve suspension in the light valve, the particles become aligned and for many suspensions most of the light can pass through the cell. Light valves have been proposed for many purposes including, e.g., alpha-numeric displays, television displays, windows, mirrors, eyeglasses and the like to control the amount of light passing therethrough.
My United States patent application filed concurrently herewith, entitled Light Valve Employing A Film Comprising an Encapsulated Liquid Suspension, And Method Of Making Such Film, Ser. No. 972,826, filed Nov. 6, 1992, is incorporated herein by reference thereto. That application describes a film suitable for use in a light valve, comprising a cross-linked polymer matrix having droplets of a light valve suspension distributed in the cross-linked polymer matrix, the light valve suspension comprising particles suspended in a liquid suspending medium. The particles exhibit random Brownian movement in the absence of an electric field applied to the light valve suspension and become aligned in the presence of an electric field applied to the light valve suspension.